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Abstract:

A backlight source and a thinning method for the same are provided. The
backlight source includes: a solid state light source array having a
plurality of solid state light sources (1) distributed on the base, a
light transmitting unit (3) arranged above the solid state light source
array, and a plurality of light adjusting units (2) arranged between the
solid state light source array and the light transmitting unit (3). The
plurality of the light adjusting units (2) is arranged above the
plurality of solid state light sources (1) to reflect the shallow angle
incident light from the solid state light source (1), thus changes the
light intensity distribution of the output light through the light
transmitting unit (3) from the solid state light sources (1) from
Lambertian distribution to main sides emission.

Claims:

1. A method for making a backlight source with reduced thickness,
comprising: placing a solid state light source array including a
plurality of solid state light sources below a light transmitting unit;
wherein the light emitted by the solid state light sources are
transmitted through the light transmitting unit as an output light of the
backlight source; placing a plurality of light adjusting units between
the solid state light source array and the light transmitting unit, above
the plurality of solid state light sources, wherein each light adjusting
unit includes an edge-emitting filter plate or film which reflects
incident lights having incident angles smaller than a threshold angle and
transmits incident lights having incident angles larger than or equal to
the threshold angle, wherein each light adjusting unit spatially
corresponds to one solid state light source; and providing, between the
edge-emitting filter plates or films and the solid state light sources, a
low refractive index medium having a refractive index below 1.3, wherein
a distance between each light adjusting unit and the corresponding solid
state light source is less than 1/5 of a bounding circle diameter of a
light emitting area of the solid state light source, and wherein each
light adjusting unit reflects small-angle emitted light from the solid
state light source back to the solid state light source, wherein the
solid state light source reflects or scatters the light reflected from
the light adjusting unit back to the light adjusting unit at various
angles, whereby a spatial distribution of light intensity of the light
from the solid state light sources to the light transmitting unit is
adjusted by the light adjusting units.

2. (canceled)

3. The method of claim 1, wherein the solid state light source array
includes a plurality of solid state light sources emitting lights of
different wavelengths; and wherein each edge-emitting filter plate or
film selectively transmits incident light within a predetermined
wavelength range, the predetermined wavelength range corresponding to a
wavelength range of lights emitted by the solid state light source which
spatially corresponds to the edge-emitting filter plate or film.

4. The method of claim 1, wherein the plurality of solid state light
sources emit lights of the same wavelength, and wherein the plurality of
edge-emitting filter plates or films are spatially joined to form one
plate or film.

5. (canceled)

6. The method of claim 1, further comprising providing an air gap between
the edge-emitting filter plates or films and the solid state light
sources.

7. The method of claim 1, wherein the light transmitting unit is a light
transmitting plate having a plurality of recesses, each recess being
located to accommodate one edge-emitting filter plate or film and one
corresponding solid state light source.

8. The method of claim 7, wherein a thickness of the light transmitting
plate is less than 5 mm.

9.-11. (canceled)

12. A backlight source comprising: a base; a solid state light source
array including a plurality of solid state light sources disposed on the
base; a light transmitting unit disposed above the solid state light
source array; a plurality of light adjusting units disposed between the
solid state light source array and the light transmitting unit, wherein
each light adjusting unit includes an edge-emitting filter plate or film
which reflects incident lights having incident angles smaller than a
threshold angle and transmits incident lights having incident angles
larger than or equal to the threshold angle, wherein each light adjusting
unit spatially corresponds to one solid state light source; and a low
refractive index medium having a refractive index below 1.3 disposed
between the edge-emitting filter plates or films and the solid state
light sources, wherein a distance between each light adjusting unit and
the corresponding solid state light source is less than 1/5 of a bounding
circle diameter of a light emitting area of the solid state light source,
wherein each light adjusting unit reflects small-angle emitted light from
the solid state light source back to the solid state light source, and
wherein the solid state light source reflects or scatters the light
reflected from the light adjusting unit back to the light adjusting unit
at various angles, whereby a spatial distribution of light intensity of
the light from the solid state light sources to the light transmitting
unit is adjusted by the light adjusting units.

13. The backlight source of claim 12, wherein the light transmitting unit
is a light transmitting plate with a predetermined a thickness wherein
the edge-emitting filter plate is disposed adjacent the light
transmitting plate or the edge-emitting filter film is coated on the
light transmitting plate.

14. The backlight source of claim 12, wherein the plurality of solid
state light sources emit lights of the same wavelength, and wherein the
plurality of edge-emitting filter plates or films are spatially joined to
form one plate or film.

15. The backlight source of claim 13, wherein the light transmitting
plate has a plurality of recesses on its bottom, the light transmitting
plate cooperating with the base to accommodate one edge-emitting filter
plate or film and one corresponding solid state light source in each
recess.

16.-20. (canceled)

21. A liquid crystal display device comprising a liquid crystal panel and
a backlight source, wherein the backlight source comprises: a base; a
solid state light source array including a plurality of solid state light
sources disposed on the base; a light transmitting unit disposed above
the solid state light source array; a plurality of light adjusting units
disposed between the solid state light source array and the light
transmitting unit, wherein each light adjusting unit spatially
corresponds to one solid state light source, wherein each light adjusting
unit includes an edge-emitting filter plate or film which reflects
incident lights having incident angles smaller than a threshold angle and
transmits incident lights having incident angles larger than or equal to
the threshold angle; and a low refractive index medium having a
refractive index below 1.3 disposed between the edge-emitting filter
plates or films and the solid state light sources, wherein a distance
between each light adjusting unit and the corresponding solid state light
source is less than 1/5 of a bounding circle diameter of a light emitting
area of the solid state light source, wherein each light adjusting unit
reflects small-angle emitted light from the solid state light source back
to the solid state light source, and wherein the solid state light source
reflects or scatters the light reflected from the light adjusting unit
back to the light adjusting unit at various angles, whereby a spatial
distribution of light intensity of the light from the solid state light
sources to the light transmitting unit is adjusted by the light adjusting
units.

22. The liquid crystal display device of claim 21, wherein the light
transmitting unit is a light transmitting plate with a predetermined a
thickness wherein the edge-emitting filter plate is disposed adjacent the
light transmitting plate or the edge-emitting filter film is coated on
the light transmitting plate.

23. The liquid crystal display device of claim 21, wherein the plurality
of solid state light sources emit lights of the same wavelength, and
wherein the plurality of edge-emitting filter plates or films are
spatially joined to form one plate or film.

24.-25. (canceled)

Description:

[0001] This is a U.S. National Stage application of PCT/CN2010/000990,
filed Jul. 1, 2010, which claims priority from Chinese patent application
CN 200910108498.2, filed Jul. 1, 2009, both of which are herein
incorporated by reference in their entireties.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to a device to control the intensity or
direction of light from independent light sources, and in particular,
such a device useful in a backlight source of liquid crystal display
(LCD) devices.

[0004] 2. Description of the Related Art

[0005] A typical LCD device includes a light source system with a number
of monochromatic light sources, such as and not limited to, red light
source, green light source, and blue light source, generating red (R),
green (G), and blue (B) lights, respectively. Because the liquid crystal
can only modulate the light intensity but cannot produce light itself,
the light source system is generally a surface light source that is
placed behind and illuminates the liquid crystal panel, commonly referred
to as backlight source.

[0006] Currently, the following schemes of LCD devices and their backlight
sources are in use.

[0007] The first one uses a light source side-coupling method. Its
structural mechanism is shown in FIG. 1. The light source is placed at
the side of a wedge-shaped light guide plate. The upper surface of this
light guide plate generally has some microstructures for light
scattering. This way, when the light is injected into the light guide
plate from the side, it transmits out from the upper surface while
propagating forward, and enters transmission type or
semi-transmission/semi-reflection type liquid crystal panel 4. The
microstructures help to scatter the outgoing light from the surface light
source. The light source can be cold-cathode fluorescent lamps (CCFL)
often used in traditional CCFL displays, or solid state light source,
such as and not limited to, light emitting diodes (LED). For example, for
most of today's mobile phones, the backlights of their liquid crystal
screen use white LEDs.

[0008] The second scheme is the light source back-coupling method. Its
structural mechanism is shown in FIG. 2. A light source, for example an
array of LEDs 1, is placed at the back of the liquid crystal panel 4 to
illuminate the liquid crystal panel directly. To solve the problem of
uniformity of the outgoing light from the surface light source, a
scattering body 51 and a scattering surface 52 are often inserted in
between the array of LEDs 1 and the liquid crystal panel 4 to form a
sufficiently large scattering space to achieve a uniform distribution of
the outgoing light. U.S. Pat. No. 7,052,152 B2 discloses such a backlight
source which also includes a layer of wavelength conversion material. The
wavelength conversion material converts excitation light from the array
of LEDs into excited light and provides the excited light to illuminate
the liquid crystal panel. This patent also discloses various electrical
connections of respective LED in the array of LEDs.

[0009] The third scheme is a combination of the light source side-coupling
and the light source back-coupling method. For example, Chinese patent
application No. 03123095 discloses a backlight module including a light
guide plate, a side light source, and a back light source.

[0010] There are shortcomings for the existing techniques mentioned above.
For the first scheme of using light source side-coupling method, it is
difficult for the light guide plate to ensure that the liquid crystal
panel is uniformly illuminated when the size of liquid crystal panel is
large. The display brightness of the portion of the screen that is far
away from the side light source is especially difficult to be controlled
or guaranteed. Even adopting double side-coupling for improvement, the
size of the liquid crystal panel is still limited due to the
non-uniformity of display brightness. Besides, the total thickness of
this type of backlight source depends on the width of the light source
and the thickness of the light guide plate, and thus it is difficult to
make it ultra thin.

[0011] For the second scheme of using light source back-coupling method,
although it can overcome the screen size-limit problem mentioned above,
the necessary existence of the scattering body or the scattering space
not only reduces the light transmission efficiency but also increases the
total thickness of the backlight module. If the scattering body or the
scattering space is reduced in order to make the device ultra thin, the
occurrence of red, blue or green light spots may be unavoidable due to
the insufficient mixture of red, green, and blue light.

[0012] For the third scheme of combining the side-coupling and the
back-coupling method, although it overcomes the shortcoming of the
previous two methods, there is still some degree of thickness requirement
for the backlight source.

SUMMARY OF THE INVENTION

[0013] The present invention aims to solve the technical problems and the
shortcomings of the existing technologies mentioned above. Embodiments of
the present invention provide a backlight source and a method to reduce
its thickness which substantially eliminates the size limitation of the
liquid crystal panel and minimizes the thickness of the backlight source
so as to reduce the overall thickness of the LCD device, without
compromising the uniformity of the outgoing light.

[0014] To address the above technical problems, the basic principles of
the present invention are as followings. To make backlight sources
adaptable to different sizes of liquid crystal panels, it is preferred to
use solid state light sources, such as arrays of LEDs, and use
back-coupling. Since the intensity of light emitted from LEDs generally
follows the Lambertian distribution (cosine distribution), existing
technologies use a large enough scattering space to ensure the uniform
illumination of liquid crystal panels and prevent the occurrence of light
spots. In embodiments of the present invention, the above light
distribution is changed by reducing the intensity of small angle outgoing
light and increasing the intensity of large angle outgoing light. Because
large angle light has a longer light path and a larger range of
irradiation when propagating forward, the uniform mixture of red, green,
and blue light can be achieved in a smaller scattering space, which can
reduce the thickness of the backlight source.

[0015] To achieve these and other advantages and in accordance with the
purpose of the present invention, as embodied and broadly described, the
present invention provides a method for making a backlight source with
reduced thickness, which includes: placing a solid state light source
array including a plurality of solid state light sources below a light
transmitting unit; wherein the light emitted by the solid state light
sources are transmitted through the light transmitting unit as an output
light of the backlight source; and placing a plurality of light adjusting
units between the solid state light source array and the light
transmitting unit, above the plurality of solid state light sources,
wherein each light adjusting unit spatially corresponds to one solid
state light source to reflect small-angle emitted light from the solid
state light source back to the solid state light source, wherein the
solid state light source reflects or scatters the light reflected from
the light adjusting unit back to the light adjusting unit at various
angles, whereby a spatial distribution of light intensity of the light
from the solid state light sources to the light transmitting unit is
adjusted by the light adjusting units.

[0016] More specifically, a distance between the light adjusting unit and
the corresponding solid state light source is between 1/5 and 1/10 of a
bounding circle diameter of the light emitting area of the solid state
light source. Each light adjusting unit includes an edge-emitting filter
plate or film which reflects incident lights having incident angles
smaller than a threshold angle and transmits incident lights having
incident angles larger than or equal to the threshold angle. When the
solid state light source array includes a plurality of solid state light
sources emitting lights of different wavelengths, each edge-emitting
filter plate or film selectively transmits incident light within a
predetermined wavelength range, the predetermined wavelength range
corresponding to a wavelength range of lights emitted by the solid state
light source which is spatially corresponded to the edge-emitting filter
plate or film. When the plurality of solid state light sources emit
lights of the same wavelength, the plurality of edge-emitting filter
plates or films are spatially joined to form one plate or film. Further,
a low refractive index medium having a refractive index below 1.3 is
provided between the edge-emitting filter plates or films and the solid
state light sources; or an air gap is provided between the edge-emitting
filter plates or films and the solid state light sources. The light
transmitting unit may be a light transmitting plate having a plurality of
recesses, each recess being located to accommodate one edge-emitting
filter plate or film and one corresponding solid state light source. The
thickness of the light transmitting plate can be less than 5 mm.

[0017] In one embodiment, each light adjusting unit includes a reflector
disposed at a predetermined distance above a corresponding solid state
light source to reflect small-angle lights from the solid state light
source, and one or more reflective surfaces are provided between the
plurality of solid state light sources or below the plurality of solid
state light sources. Each reflector has an area substantially the same as
an light emitting area of the corresponding solid state light source, and
a distance between the reflector and the corresponding solid state light
source is between 1/5 and 1/10 of a bounding circle diameter of the light
emitting area of the solid state light source.

[0018] In another aspect, the present invention provides a backlight
source which includes: a base; a solid state light source array including
a plurality of solid state light sources disposed on the base; a light
transmitting unit disposed above the solid state light source array; and
a plurality of light adjusting units disposed between the solid state
light source array and the light transmitting unit, wherein each light
adjusting unit spatially corresponds to one solid state light source to
reflect small-angle emitted light from the solid state light source back
to the solid state light source.

[0019] More specifically, the light transmitting unit is a light
transmitting plate with a predetermined a thickness, and each light
adjusting unit includes an edge-emitting filter plate disposed adjacent
the light transmitting plate or an edge-emitting filter film coated on
the light transmitting plate, to reflect incident lights having incident
angles smaller than a threshold angle and transmits incident lights
having incident angles larger than or equal to the threshold angle. When
the plurality of solid state light sources emit lights of the same
wavelength, the plurality of edge-emitting filter plates or films are
spatially joined to form one plate or film. The light transmitting plate
has a plurality of recesses on its bottom, the light transmitting plate
cooperating with the base to accommodate one edge-emitting filter plate
or film and one corresponding solid state light source in each recess. A
distance between each edge-emitting filter plate or film and the
corresponding solid state light source is less than 1/5 of a bounding
circle diameter of a light emitting area of the solid state light source.

[0020] In one embodiment, the light transmitting unit is a light
transmitting plate with a predetermined thickness and having a plurality
of recesses on its bottom, the light transmitting plate cooperating with
the base to accommodate one light adjusting unit and one corresponding
solid state light source in each recess; each light adjusting unit
includes a first reflector plate disposed adjacent a bottom of the
corresponding recess or a first reflective film coated on the bottom of
the corresponding recess; and the backlight source further includes
either a second reflective film coated on either the light transmitting
plate or the base at locations where the light transmitting plate and the
base contact each other, or a second reflector plate sandwiched between
the light transmitting plate and the base. A distance between each light
adjusting unit and the corresponding solid state light source is between
1/5 and 1/10 of a bounding circle diameter of the light emitting area of
the solid state light source.

[0021] In one embodiment, the base has polished surfaces or reflective
regions formed of a reflective material located in spaces between the
plurality of solid state light sources; the plurality of light adjusting
units include a plurality of reflective regions formed on a light
transmitting plate; and the light transmitting unit is a diffuser plate
located above the light transmitting plate. The backlight source further
includes a transparent material disposed between the base and the light
transmitting plate.

[0022] In another aspect, the present invention provides a liquid crystal
display device which includes a liquid crystal panel and a backlight
source as described above.

[0023] It is to be understood that both the foregoing general description
and the following detailed description are exemplary and explanatory and
are intended to provide further explanation of the invention as claimed.

[0026] FIG. 3 schematically illustrates a backlight source of a LCD device
according to a first embodiment of the present invention.

[0027] FIG. 4 schematically illustrates an edge-emitting filter used in
the embodiment of FIG. 3.

[0028] FIG. 5 schematically illustrates a backlight source of a LCD device
according to a second embodiment of the present invention.

[0029] FIG. 6 schematically illustrates a backlight source of a LCD device
according to a third embodiment of the present invention.

[0030] FIG. 7 schematically illustrates a backlight source of a LCD device
according to a fourth embodiment of the present invention.

[0031] FIG. 8a is a plan view of the reflective plate 7 in FIG. 7.

[0032] FIG. 8b is a plan view of the reflective plate 6 in FIG. 6.

[0033] FIG. 9 shows an example of light transmission characteristics of
the edge-emitting filter for the blue LED in FIG. 3.

[0034] FIG. 10 shows a comparison of the outgoing light distribution for
the LED in FIG. 8 with and without the filter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] Embodiments of the present invention are described in more detail
below with reference to the drawings.

[0036] As described earlier, a method for a conventional backlight source
to provide outgoing light includes the following steps:

[0037] Providing a backlight source by placing an array of a plurality of
solid state light sources below a light transmitting unit. The solid
state light source may be an LED but is not limited thereto. The light
transmitting unit may be a light guide plate but is not limited thereto.

[0038] Light emitted from the solid state light source transmits through
the light transmitting unit, and provides outgoing light of the backlight
source.

[0039] To reduce the thickness of a backlight source, a method according
to embodiments of the present invention improves upon the above described
method as follows:

[0040] Between the array of solid state light sources and the light
transmitting unit, a plurality of light adjusting units are placed above
the plurality of the solid state light sources. Each light adjusting unit
corresponds in position with one solid state light source and reflects
small angle incident light from the solid state light source, so that
light intensity distribution of outgoing light of the light transmitting
unit changes from a Lambertian distribution (containing mainly small
angle outgoing light, as shown in the characteristics curve in FIG. 10)
to a distribution containing mainly large (wide) angle outgoing light. In
particular, the small angle incident light from the solid state light
sources is reflected back to the array of solid state light sources. When
such light is reflected or scattered by the array of solid state light
sources back to the light adjusting units, its incident angle is changed.
After one or more such cycles, the light is eventually outputted as large
angle light. This improves or ensures the brightness of the light source.

[0041] A backlight source according to embodiments of the present
invention includes a solid state light source array having a plurality of
solid state light sources distributed on a base, a light transmitting
unit arranged above the solid state light source array, and a plurality
of light adjusting units disposed between the solid state light source
array and the light transmitting unit. Each light adjusting unit
corresponds in position with one solid state light source in order to
reflect small angle incident light from the solid state light source.

[0042] FIG. 3 and FIG. 5 illustrate two backlight sources according to
embodiments of the present invention. The array of solid state light
sources 1 is distributed on the base (not shown). The light transmitting
unit may be the light transmitting plate 3 with a certain thickness. The
light adjusting units may be edge-emitting filter plates or films to
reflect the incident light having incident angles less than a threshold
angle and transmit light having incident angles greater than or equal to
the threshold angle. This light adjusting unit can be the edge-emitting
filter 2 disposed immediately adjacent to the light transmitting plate 3
as shown in FIG. 3, or it can be an edge-emitting film 2' coated on the
light transmitting plate as shown in FIG. 5. In the structure of FIG. 3,
to make the backlight module as thin as possible, the light emitting
plate 3 is provided with a plurality of recesses. The edge-emitting
filter plates 2 and the solid state light sources 1 are disposed inside
the corresponding recesses.

[0043] FIG. 4 schematically illustrates the operation of an edge-emitting
filter plate. Wider angle incident lights from solid state light sources,
such as and not limited to, LEDs, penetrate the edge-emitting filter 2,
while smaller angle incident lights will be reflected by edge-emitting
filter 2 back to LED surface and are scattered or diffused by the LED
surface. Smaller angle incident lights are recycled multiple times in
this manner between the LED surface 1 and the edge-emitting filter 2. The
light may be lost or eventually penetrate the edge-emitting filter 2 as
wider angle light. After light is recycled in this manner, the wide angle
light emitted by the LED toward the light transmitting plate 3 can be
greatly enhanced. Having too large a distance between the solid state
light source 1 and the edge-emitting filter plate 2 is undesirable for
large-angle output of lights from peripheral areas of the solid state
light sources. Thus, methods according to embodiments of the present
invention control the distance between the edge-emitting filter plate or
film and the solid state light sources. Test calculations show that this
distance should be less than 1/5 of a bounding circle diameter of the
solid state light source and, the smaller the better.

[0044] An array of solid state light sources for projection display
systems often includes solid state light sources emitting at multiple
different wavelengths. In order to achieve better mixture of lights to
obtain a more uniform light, the edge-emitting filter plate or film
according to embodiments of the present invention also has selective
light transmission characteristics based on the wavelength of the
incident lights. The selected transmission wavelength range of a filter
corresponds to the wavelength range of the light emitted by the
corresponding solid state light source. FIG. 9 shows an example of light
transmission characteristics of an edge-emitting filter plate 2 for a
blue LED. As shown in this figure, light emitted from the blue LED is
concentrated in the 450 nm range. In this range, the edge-emitting filter
plate 2 mainly reflects incident lights with incident angles between 0 to
40 degrees, while its light transmission efficiency increases
significantly for lights with incident angles over 40 degrees (e.g. 60 or
80 degrees). Therefore, as shown in FIG. 10, the light intensity of light
originally emitted from the blue LED has a Lambertian distribution; i.e.,
the wider the angle of outgoing light is, the smaller the light
intensity. Due to the effect of the edge-emitting filter plate 2, the
distribution of the outgoing blue light changes into a distribution
containing mainly light having output angle between 40 to 70 degrees.
This way, the length of the light path of the blue light in the light
transmitting plate increases greatly compared to the existing technology,
and thus uniform mixture of lights can be achieved through propagations
of just a few times.

[0045] If a display system only requires a monochromatic backlight source,
the multiple solid state light sources have the same wavelength. In such
a case, in a backlight source according to embodiments of the present
invention, as shown in FIG. 5, the edge-emitting filter film 2' or the
edge-emitting filter plate 2 can be merged into a single piece (not shown
in the drawing).

[0046] In the above embodiments, based on cost concerns, the light
transmitting plate 3 may be a plastic plate functioning as a support for
the LCD panel 4. When the size of the LCD panel is relatively small, the
light transmitting plate can be replaced by an air gap, which can be
formed by using a number of support posts on the LCD panel 4.

[0047] The thickness of the LED chips is typically very small, such as
about 0.1 mm. The light transmitting plate 3 may be provided with a
plurality of recesses, as shown in FIG. 3, where the light transmitting
plate 3 cooperates with the base to accommodate the light adjusting units
and the solid state light sources in the recesses. As a result, the
entire thickness of the backlight source can be less than 5 mm, achieving
an ultra-thin backlight source.

[0048] In embodiments of the present invention, to reduce the thickness of
the backlight source, the edge-emitting filter plates or films may be
disposed immediately adjacent the solid state light sources. To increase
the brightness of the backlight source, a low refractive index medium
having a refractive index below 1.3 may be provided to fill the space
between the edge-emitting filter plates or films and the solid state
light sources. The low refractive index medium may be, for example, glue.
Considering that filling with glue may cause the light emitting area of
the solid state light sources to increase, resulting in reduced
brightness, and considering that the refractive index of air is 1, an
alternative approach is to provide an air gap between the edge-emitting
filter plates or films and the solid state light sources. This can
maximize the brightness of the solid state light sources.

[0049] According to another embodiment of the present invention, in lieu
of edge-emitting filter plates, a first set of reflectors may be disposed
at a desired distance above the solid state light sources to reflect
small angle lights from the solid state light sources. Correspondingly, a
second reflecting surface is disposed between the array of solid state
light sources of below them, to reflect the lights reflected by the first
set of reflectors back to the light transmitting unit. This way, large
angle lights from the solid state light sources will be reflected out by
the first set of reflectors, and small angle lights are reflected back to
the solid state light sources where the light is scattered. The
scattering changes the angle of the light, so that some lights become
large angle lights and can be output.

[0050] FIG. 7 illustrates a backlight source using the principle describes
above. In this embodiment, the light transmitting unit is a light
transmitting plate 3 with a predetermined a thickness and having a
plurality of recesses on its bottom. The light transmitting plate 3
cooperates with the base to accommodate the light adjusting units and the
corresponding solid state light sources in the corresponding recesses.
The light adjusting unit is a reflector 6 disposed immediately adjacent a
bottom of the recess or a reflecting film coated on the bottom surface of
the recess. In areas where the light transmitting plate 3 contacts the
base, the light transmitting plate 3 or the base is coated with a
reflecting film 7; alternatively, a reflecting plate may be sandwiched
between the light transmitting plate 3 and the base.

[0051] In this structure, controlling the distance between the light
adjusting unit (reflector 6) and the solid state light sources is
critical. Preferably, the reflecting area of the reflector is set at
approximately the same or slightly larger than the light emitting area of
the solid state light source. To obtain output lights from the solid
state light source with output angles greater than 60 degrees, for a LED
chip having a bounding circle diameter L, the above distance should be
between L/5 to L/10. FIG. 8a illustrates a plan view of a reflector 7
sandwiched between the light transmitting plate 3 and the base, where the
multiple small rectangles correspond to an area reserved for the LEDs.

[0052] FIG. 6 illustrates an alternative structure according to another
embodiment of the present invention. The base has a polished surface
between the solid state light sources, or reflective regions formed by a
reflective material between the solid state light sources, as indicated
by the shaded areas in the plan view of FIG. 8a. A light transmitting
plate 6' is supported above the base, and has a structure in a plan view
as shown in FIG. 8b. The light transmitting plate 6' has a plurality of
areas coated with a reflective material as shown by the shaded areas in
FIG. 8b, which function as the light adjusting units. A diffuser plate 52
is supported above the light transmitting plate 6' and functions as the
light transmitting unit. In addition, a transparent body formed of a
transparent material may be disposed in or fills the space between the
diffuser plate 52 and the light transmitting plate 6'.

[0053] According to embodiments of the present invention, the distance
between the diffuser 52 and the base in FIG. 6, or the thickness of the
light transmitting plate 3 in FIG. 7, can be smaller than 5 mm.

[0054] The backlight source according to embodiments of the present
invention can be used in a LCD device, which includes an LCD panel and
the backlight source. The overall thickness of the LCD device can be
reduced using such a backlight source.

[0055] It will be apparent to those skilled in the art that various
modification and variations can be made in the backlight source and
related method of the present invention without departing from the spirit
or scope of the invention. Thus, it is intended that the present
invention cover modifications and variations that come within the scope
of the appended claims and their equivalents.